Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-1-
Title
Washer and threaded fastener assembly incorporating same
Field of the Invention
This invention relates to a washer for a threaded fastener assembly for
securing
a work-piece in position. The invention also relates to a threaded fastener
assembly and in particular to a threaded fastener assembly that opposes
unintentional off-torque. The term "off-torque" as used herein is intended to
refer
to torque applied to a threaded fastener assembly to loosen or unthread the
assembly. The invention also concerns proper fastener preloading and the
ability to maintain that load.
Background of the Invention
Four major factors dramatically contribute to the failure of known threaded
fasteners; namely: inappropriate preload; creep in all the components of the
joint
established by the threaded fastener; environmentally generated off-torque;
and
elevated and differential temperature.
Various designs have been proposed to solve these deficiencies, however
failure
of threaded joints continue to persistently occurs in almost every industry
leading
to loss of life, damage to equipment and other property including loss of
product,
production delays, and environmental disasters.
Wedge fasteners have been proposed in various forms to counteract a vibration
or shock generated off-torque. Typically, such wedge fasteners utilise a
washer
to engage a surface of the work-piece with increased friction. However, the
configuration of the washer can have the effect of damaging the work-piece
surface with which it engaged, as well as causing accelerated creep at an
increased magnitude and preventing accurate preloading. A design that
operates without a frictional surface has been proposed in US 4,793,752.
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-2-
However, it requires an extensive flange for its operation. A design that
employs
ratchet teeth for easy preloading is disclosed in US 4,034,788. It, however,
requires the use of locking teeth that embed themselves into a work-piece.
A self-centring feature has been proposed for fasteners disclosure in US
3,241,589, US 3,926,237 and US 4,283,091. Loading of the proposed fasteners
is likely to be highly uncertain due to work-piece embedding teeth and linear
contact between a washer and a threaded fastener.
In certain applications, it is important for fasteners to be loaded to a
specified
torque in order to ensure that a desired holding force is developed within the
joint. Precision loading of a fastener to achieve a prescribed torque can be
difficult to achieve. The most common method currently in practice, which has
an accuracy of 25%, involves use of a torque wrench. Angle controlled
tightening, which has a 15% accuracy, requires skilful labour to be properly
applied. An example of such is disclosed in US 5,165,831. The method bears
some of the deficiencies of the torque wrench as it requires in its first step
the
application of a snug torque. 'Turn of the screw' method is disclosed in US
3,851,386, involving finger tightening in the first step and alignment with
predetermined position 'that looks and feels right' but which is less than
elongation of failure. Although providing a highly satisfactory solution, a
fastener
incorporating a scale, such as the fastener disclosed in US 5,411,008, is
limited
to the application on which it is employed.
Precision loading is particularly important where fasteners cooperate in a
circular
array. For securing wheels, a 'quarter turn' method is in common use where a
quarter turn at a time is applied in a crisscross sequence. For flanges,
several
passes of a 'four point star' are often applied. More accurate loading can be
achieved by the method disclosed in US 5,278,775.
In relation to motor-aided applications, flange nuts mounted on a spindle of a
power tool suffer thread profile permanent deformation when subject to high
torque. The effect is particularly severe in tools of a larger diameter, such
as
cutting or grinding discs. Hand operated nuts that correct the problem have
PCT/AU01; OO~JJ
CA 02439416 2003-09-09 Received 11 March 200?
-3-
appeared recently on the market. A variety of designs have been proposed (for
example as in US 5,89C~,Ei48), but component parts numbering usually in excess
of 20 and complexity of manufacturing render such hand-operated nuts
uneconomical for separate sale and they are usually sold as a part of a power
tool.
It has been recently acH:nowledged that addition of a cone spring washer to
the
fastener assembly effectively counteracts creep Various designs have been
proposed, several exarmples of which can be seen in US 5,547.326 and
5,597,279. None of the proposals, however considers how such a washer aids
off-torque after a certain amount of creep lifts the central portion off' the
work-
piece.
It is against this background, and the problems and deficiencies associated
therewith, that the present invention has been developed.
Disclosure of the In~rention
The present invention provides a washer for a threaded fastener assembly
having an engaging zone at which a component of the assembly is subjected to
frictional engagement without protrusions, the washer comprising a body having
a central axis including two opposed sides. an outer periphery, an inner
periphery defining a central aperture extending between the two opposed sides,
a ramp structure for interaction with further components of the threaded
fastener
assembly to provide a mechanical connection therebetween for resisting
unthreading of the threaded fastener assembly. the relative positions of the
engaging zone and the ramp strcrcture being :such that in use torque
transferred
through the engaging zone is greater than torque acting through the ramp
structure limiting or eliminating possible damacle to the work-piece surface.
It is advantageous to form the washer in such a manner that the resultant
vector
of fastener forces transferred through the ramp structure is located closer to
the
central axis than the re~;ultant vector of fricaional forces acting through
the
engaging zone
~AMENIOECy .~hIF;~'~
m~~ s.
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-4-
Typically, this is achieved by locating the ramp structure closer to the
central axis
than the engaging zone. The ramp structure and the engaging zone may be
spaced along the radius from each other or there may be over-lapping
therebetween.
The ramp structure may comprise a ramp profile incorporating wedge ramps or
ratchet teeth.
The ramp structure may comprise a plurality of ramp sections each having a
sloping ramp face and an abutment face. Each slopping face is preferably
inclined with respect to a plane transverse to said central axis thereby to
provide
a self-centering action.
In a typical application, the ramp structure on the body of the washer would,
in
use, interact with a further ramp structure on another component within the
threaded fastener assembly. The ramp structure on the body of the washer will
hereinafter be referred to as the "base ramp structure" and the further ramp
structure will hereinafter be referred to as the "mating ramp structure".
The base ramp structure and the mating ramp structure may each have a ramp
profile adapted to interact with the other to resist unthreading of the
threaded
fastener assembly. The interacting ramp profiles can be of the same or similar
mating configurations.
The further component of the threaded fastener assembly with which, in use,
the
base ramp structure interacts may comprise a threaded fastener, such as the
head of a bolt, screw, or a nut, having a mating ramp structure, or a further
washer constructed in accordance with the invention.
The washer may comprise an engaging face on one of the opposed sides or an
outer edge of that side constructed for operation within the engaging zone of
the
fastener assembly. In a typical situation, the washer may be located against a
work-piece in which case the engaging face frictionally engages the work-
piece.
PCTiAU01 /002~~
CA 02439416 2003-09-09 Received 11 March 2002
_6_
unthreading of a threaded fastener assembly in which the two washers are
installed. The intermediate washers of the assembly may include the engaging
faces. although this is not always the case.
Where two or more spring washers are used in the threaded fastener assembly,
they may be arranged in a series relationship, a parallel relationship, or a
relationship in which the Hrashers are arranged in a variety of series and
parallel
combinations
The invention also provides a threaded fastener assembly incorporating a
washer in accordance wil:h the invention as defined above
~o Summary of the invention
The present invention also provides a washer for a threaded fastener assembly
comprising a body having a central axis rncled~ng two opposed sides, an outer
periphery, an inner periphery defining a central aperture extending between
the
two opposed sides, an engaging face. without protrusions, for lfrictionally
engaging a component e:rf the threaded fastener assembly or a worl~c-piece, a
ramp structure disposed between the inner periphery and one of the opposed
sides for interacting with <~ further component of the threaded fastener
assembly
to provide a mechanical connection there between for resisting unthreading of
the
threaded fastener assemt~l~r the engaging face being associated with the other
of the opposed sides and extending circumferentiafly about the central axis,
the
relati~re positions o' the engaging face and the ramp structure veith respect
to the
central axis being such that m use torque transferred through the engaging
face
is greater than torque actirng through the ramp structure.
With the arrangement, the resultant vector of fastener loading forces
transferred
through the ramp structure is located closer to the central axes than the
resultant
vector of frictional forces aeaung through the engageng face.
Typically, the relative posptions are such that the ramp structure is
positioned
closAr to the central axis l:h~~f~ the engaging tace The ramp structure and
the
A~MENDEt'R ~NC~
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-6-
unthreading of a threaded fastener assembly in which the two washers are
installed. The intermediate washers of the assembly may include the engaging
faces, although this is not always the case.
Where two or more spring washers are used in the threaded fastener assembly,
they may be arranged in a series relationship, a parallel relationship, or a
relationship in which the washers are arranged in a variety of series and
parallel
combinations.
The invention also provides a threaded fastener assembly incorporating a
washer in accordance with the invention as defined above.
1o Summary of the Invention
The present invention also provides a washer for a threaded fastener assembly
comprising a body having a central axis including two opposed sides, an outer
periphery, an inner periphery defining a central aperture extending between
the
two opposed sides, an engaging face for frictionally engaging a component of
the threaded fastener assembly or a work-piece, a ramp structure disposed
between the inner periphery and one of the opposed sides for interacting with
a
further component of the threaded fastener assembly to provide a mechanical
connection therebetween for resisting unthreading of the threaded fastener
assembly, the engaging face being associated with the other of the opposed
sides and extending circumferentially about the central axis, the relative
positions
of the engaging face and the ramp structure with respect to the central axis
being
such that in use torque transferred through the engaging face is greater than
torque acting through the ramp structure.
With the arrangement, the resultant vector of fastener loading forces
transferred
through the ramp structure is located closer to the central axes than the
resultant
vector of frictional forces acting through the engaging face.
Typically, the relative positions are such that the ramp structure is
positioned
closer to the central axis than the engaging face. The ramp structure and the
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-7-
engaging face may be radially spaced from each other or there may be some
over lapping there between.
The engaging face may be on said other of the opposed sides or an outer edge
of that side.
The ramp structure may comprise a ramp profile incorporating wedge ramps or
ratchet teeth.
The ramp structure may comprise a plurality of ramp sections each having a
sloping ramp face and an abutment face. Each slopping face is preferably
inclined with respect to a plane transverse to said central axis thereby to
provide
a self-centering action.
The washer may be a plane washer or a frusto-conical spring washer. Where
the washer is a plain washer, said other face may have a central recess
surrounding the central aperture thereby to form the annular engaging face.
Where the washer is a spring washer, the engaging face preferably comprises
the outer edge of the spring washer.
The washer may be configured for engagement by a tool. Alternatively, the
washer may incorporate a grip means to facilitate manual operation thereof.
The washer may, together with another component of the threaded fastener
assembly, incorporate means for providing a visual indication of the extent of
loading on the assembly.
The washer in accordance with the invention may be the only washer used in the
threaded fastener assembly, or two or more such washers may be used in the
assembly. When there is more than one washer in the assembly, a washer or
washers may be provided with two ramp structures each associated with the
opposed sides positioned for interaction with further ramp structures of other
parts of the assembly. The location of any such ramp structure within the
fastener assembly is such that in use a loading torque transferred through the
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
_$_
engaging zone is greater than the loading torque acting through the ramp
structure.
With this arrangement, the ramp structure of one washer interacts with the
further rump structure of the other washer for wedging, ratcheting or
resisting
relative rotation between the two washers in a direction corresponding to
unthreading of a threaded fastener assembly in which the two washers are
installed. The intermediate washers of the assembly may include the engaging
faces, although this is not always the case.
Where two or more spring washers are used in the threaded fastener assembly,
they may be arranged in a series relationship, a parallel relationship, or a
relationship in which the washers are arranged in a variety of series and
parallel
combinations.
The washer may be provided with a further ramp structure associated with the
other of the opposed sides, the further ramp structure being so positioned for
interaction with the ramp structure of a second washer which is in accordance
with the invention and with which it is assembled in a parallel configuration.
With
this arrangement, two washers can be assembled in a parallel configuration,
with
the ramp structure of one washer interacting with the further ramp structure
of
the other washer for resisting relative rotation between the two washers in a
direction corresponding to unthreading of a threaded fastener assembly in
which
the two washers are installed. Indeed, the further ramp structure is necessary
in
circumstances where washers are to be arranged in a parallel relationship for
otherwise there would be undesired movement between the mating washers.
The present invention also provides a threaded fastener assembly incorporating
a washer in accordance with the invention as hereinbefore defined.
The present invention further provides a threaded fastener assembly for
releasably securing a work-piece in position, the threaded fastener assembly
comprising a threaded fastener having an axis of rotation, a washer presenting
an annular engaging face concentric with said axis of rotation for
frictionally
PcTiauolioo~ss
CA 02439416 2003-09-09 Received 11 March 200?
_g_
engaging the work-piece, and means providing a mechanical connection
between the threaded fa~;tener and the washer for resisting unthreading of the
threaded fastener. said means including a ramp structure on they threaded
fastener. the ramp structure being positioned closer to the axis of rotation
of the
threaded fastener than tloe annular engaging face of the washer.
With this arrangement. the engaging face of the washer is disposed radially
further from said axis of rotat;an of the threaded fastener than the
rnechanical
connection between the threaded fastener than the washer. In this way, lower
frictional toraue is established at the mechanical connection bel:ween the
threaded fastener and I:he vu~asher than exists between the washer and the
work-piece which is frictic:mallv engaged by tt~e washer without any
protrusions.
Although not limited thereto the threaded fastener typically comprises a nut,
bolt
or screw
In one arrangement. the rrnechanical connection between the threaded fastener
and the masher may be established between the threaded fastener and the
washes
In another arrangement, the means providing a mechanical connection between
the threadea fastener grog the washer may include an intermediate member
adapted ~o be posmoned d:ae!ween the threaded fastener and the washer, the
intermediate member being mechanically connected to both the threaded
fastener and the washer.
The present invent;on also provides a threaded fastener assembly for
releasably
securing a work-piece in I:~csition, the threaded fastener assembly comprising
a
threaded fastener having an axis of rotation. a 4vasher presenting an annular
engaging .ace concentric ~n.~ith said axis o° rc7tatic7n for
frictionally engaging the
work p;ec~:. and means promding a mecha~mca~ connection between the threaded
fastener and the washer f:o resisting unthreading of the threaded fastener,
said
means having co-acting ~:~urfaces which are inclined with respect to a plane
extending rag ally w~~th reslne~' to said axis c;f rotation
AME~I~Ei~ aHE
r~~ r».: ,
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-10-
A threaded fastener assembly in accordance with the invention may further
comprise a means for providing a visual indication of the extent of loading on
the
assembly. Such means may comprise an indicator such as a pointer operating in
association with a scale. In a typical application, the indicator is provided
on the
threaded fastener. The scale may, for example, be provided on the work-piece
or on an element (such as a washer) positioned between the work-piece and the
threaded fastener. The scale may be permanently in position or separately
provided for attachment during joint installation as may be required.
Similarly the
scale can be on a threaded fastener and a pointer on a washer or work-piece.
Once the washer contacts the work-piece, the indicator is aligned with the
beginning of the scale. A torque-imposing tool can then be used to load the
assembly according to the scale.
Brief Description of the Drawings
With a substantial number of optional features of this invention a great
number of
embodiments can be constructed. The invention wilt be better understood by
reference to the following description of a number of such embodiments. The
description will be made with reference to the accompanying drawings in which:
Figure 1 is a perspective view of a washer according to a first
embodiment;
Figure 2 is an underside perspective view of the washer;
Figure 3 is a cross-section of the washer;
Figure 4 is a perspective view of a threaded fastener assembly that
incorporates the washer of the first embodiment;
Figure 5 is an underside perspective view of a nut forming part of the
threaded fastener assembly of Figure 4;
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-11-
Figure 6 is a sectional view of the threaded fastener assembly in
association with a work-piece;
Figure 7 is a perspective view of a bolt that can be substituted for the nut
in the threaded fastener assembly;
Figure 8 is a perspective view of a variant of the washer according to the
first embodiment;
Figure 9 is a perspective view of a further variant of the washer according
to the first embodiment;
Figure 10 is an underside perspective view of a nut for use with the
washer of Figure 9;
Figure 11 is a fragmentary sectional view of a threaded fastener assembly
with a washer according to a second embodiment;
Figure 12 is a cross-sectional view of the washer of the second
embodiment;
Figure 13 is a plan view of the washer;
Figure 14 is a sectional view of a nut forming part of the threaded fastener
assembly of Figure 11;
Figure 15 is a plan view of the nut shown on Figure 14;
Figure 16 is a fragmentary sectional view of an alternative threaded
fastener assembly incorporating the washer of the second embodiment;
Figure 17 is a fragmentary sectional view of a threaded fastener assembly
accommodating a washer according to a third embodiment;
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-12-
Figure 18 is an underside view of the head of a bolt forming part of the
threaded fastener assembly of Figure 17;
Figure 19 is a detailed section of the assembly of Figure 17;
Figure 20 is a section similar to Figure 19 except that the threaded
fastener assembly is shown in a fully loaded condition;
Figure 21 is a fragmentary sectional view of an alternative threaded
fastener assembly incorporating the washer of the third embodiment;
Figure 22 is a detailed section of a threaded fastener assembly with a
washer according to a fourth embodiment;
Figure 23 is a section similar to Figure 22 except that the threaded
fastener assembly is shown in a fully loaded condition;
Figure 24 is a section through an assembly with two washers according to
a fifth embodiment;
Figure 25 is a perspective view of a nut forming part of the assembly of
Figure 24;
Figure 26 is a perspective view of an intermediate washer forming part of
the assembly of Figure 24;
Figure 27 is a perspective view of a retainer washer forming part of the
assembly of Figure 24;
Figure 28 is a fragmentary section through a threaded fastener assembly
incorporating two washers of a sixth embodiment;
Figure 29 is a perspective view of a nut forming part of the threaded
fastener assembly shown in Figure 28;
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-13-
Figure 30 is a perspective view of an intermediate washer forming part of
the assembly shown in Figure 28;
Figure 31 is a perspective view of the retainer washer forming part of the
assembly shown in Figure 28;
Figure 32 is a perspective view of a threaded fastener assembly with two
washers;
Figure 33 is a perspective view of a nut forming part of a threaded
fastener assembly of Figure 32;
Figure 34 is a perspective view of the washer employed in the threaded
fastener assembly of Figure 32;
Figure 35 is a perspective view of a further washer employed in the
threaded fastener assembly of Figure 32;
Figure 36 is a section through an assembly of Figure 32;
Figure 37 is a perspective view of a bolt that can be used as an alternative
of the nut in the assembly of Figure 32;
Figure 38 is a perspective view of a size adaptor;
Figure 39 is a perspective view of a threaded fastener assembly
employing an intermediate washer and a retainer washer, the threaded
fastener assembly being shown in a first operational position;
Figures 40, 41 and 42 are views similar to Figure 39 except that the
threaded fastener assembly is shown in second, third and fourth
operational positions respectively;
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-14-
Figure 42 is a plan view of threaded fastener assembly that includes a
washer according to a further embodiment, the assembly being shown in
a first position;
Figure 44 is a section along the line 44-44 of Figure 43;
Figure 45 is a schematic view showing the relative position of ramps
within the threaded fastener assembly when in the first position;
Figure 46 is a view similar to Figure 43 with the exception that the
threaded fastener assembly is shown in a second position;
Figure 47 is a section along the line 47-47 on Figure 46;
Figure 48 is a schematic view showing the relative position of ramps
within the threaded fastener assembly when in the second position;
Figure 49 is a plan view of a threaded assembly employing an
intermediate washer and a retainer washer, with the assembly being
shown in a first position;
Figure 50 is a section along the line 50-50 of Figure 49;
Figure 51 is a schematic view showing the relative position of ramps
within the threaded fastener assembly when in the first position;
Figure 52 is a view similar to Figure 49 with the exception that the
threaded fastener assembly is shown in a second position;
Figure 53 is a section along the line 53-53 on Figure 52;
Figure 54 is a schematic view showing the relative position of ramps
within the threaded fastener assembly when in the second position;
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-15-
Figure 55 is a view similar to Figure 49 with the exception that the
threaded fastener assembly is shown in a third position;
Figure 56 is a section along the line 56-56 of Figure 55;
Figure 57 is a schematic view showing the relative position of ramps
within the threaded fastener assembly when in the third operational
position;
Figure 58 is a view similar to Figure 49 with the exception that the
threaded fastener assembly is shown in a fourth operational position;
Figure 59 is a section along the line 59-59 on Figure 58;
Figure 60 is a schematic view showing the relative position of ramps
within the threaded fastener assembly when in the fourth operational
position;
Figure 61 is a view of a loading structure for use in operating a circular
array of threaded fastener assemblies; and
Figure 62 is a view of an alternative loading structure for use in operating
a circular array of threaded fastener assemblies.
Best Models) for Carrying out the Invention
Referring now to Figures 1 to 6 of the accompanying drawings, there is shown a
threaded fastener assembly 100 incorporating a washer 390 according to a first
embodiment. The washer 390 is situated to retain a work-piece 400 in position
and hence it will be referred to as a retainer washer.
The threaded fastener assembly 100 comprises a bolt having a threaded shank
220, a threaded fastener 210 in the form of a nut, and the retainer washer
390.
The nut 210 has a thread 230, an inner face 211, an outer face 212 and an
outer
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-16-
periphery 213 of hexagonal configuration. The thread 230 is illustrated as a
conventional right-hand thread but it will be understood that a left-hand
thread
could alternatively be used. The inner face 211 of the nut 210 is provided
with
an annular ramp structure 240.
The retainer washer 390 is in the form of a plain washer having an outer
periphery 393 extending between an outer face 392 and an inner face 391. The
outer periphery 393 is of a hexagonal configuration of corresponding shape and
dimension to the hexagonal configuration of the nut 210.
The retainer washer 390 is formed of a material of hardness preferably
slightly
greater than that of the nut 210. The retainer washer 390 has an inner
periphery
declining a central aperture 394 through which the shank 220 of the bolt can
extend.
An annular ramp structure 340 is formed angularly in the retainer washer 390,
extending between the central aperture 394 and the outer face 392, as best
seen
in Figure 3. With this arrangement, the ramp structure 340 is frusto-conical
so as
to be somewhat dish-shaped. The protruding ramp structure 240 of the nut 210
is of complimentary configuration to the ramp structure 340 on the washer 390,
as best seen in Figure 5.
The dished ramp structure 340 and the protruding mating ramp structure 240
each comprise a plurality of wedge ramp sections each having a sloping face
345 and an abutment face 346, as best seen in Figure 1 of the drawings. The
sloping faces 345 are inclined in the same general direction as the thread 230
on
the nut 210 at such an appropriate angle, preferably slightly smaller than the
thread lead angle, as to cause net actual loading during unthreading of the
nut.
In addition to sloping between adjacent abutment faces 346, the ramp sections
on both the ramp structure 240 and ramp structure 340 are inclined in the
radial
direction with respect to the axis of rotation of the bolt. With this
arrangement,
the faces 345 of the ramp structure 340 formed in the retainer washer 390
slope
along the radius inwardly away from the outer face 392 and form an acute angle
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-17-
a with the axis, as best seen in Figure 3. In other words, the ramp faces are
inclined with respect to a plane extending along the radius with respect to
the
central axis of the fastener assembly. The angular configuration of the
sloping
faces 245, 345 prevents conical contact surfaces 242, 341 between the nut 210
and the retainer washer 390 respectively, making a conical force transfer
surface
between the nut 210 and the retainer washer 390. This inclination provides the
threaded fastener assembly with a self-centring action and eliminates hoop
spreading, which is a particular problem with some prior art fasteners. The
dished and protruding shape of the ramp structures 240, 340 shifts resultant
of
forces transferred closer to the centre than ramp structures situated on outer
surface of a washer and therefore allows more compact design than other known
fasteners using differential torque to resist unwanted loosening.
The inner face 391 of the retainer washer 390 has an undercut section, which
provides a central recess 397 surrounded by an engaging face 396 for
engagement against the work-piece 400. The radius at which the recess 397
ends and the engaging face 396 begins is chosen taking into consideration
frictional coefficients of abutting surfaces of the washer 390 and the work-
piece,
and friction between the washer 390 and the nut 210 on their mating ramp
sections, ramp as well as the lead angle of the ramp sections along their
travel.
In effect, lower frictional torque is established at the inter-engagement
between
the nut 210 and fihe retainer washer 390 than exists at the engaging face 396
with the work-piece. With the retainer washer 390 positioned on the shank 220
of a bolt to form the threaded fastener assembly 100 as shown in Figures 4 and
6, the ramp structure 240 on the nut 210 interacts with the ramp structure 340
on
the retainer washer 390, with the ramp faces of the respective ramp structures
240, 340 in mating relationship. Engagement between the nut 210 and the
retainer washer 390 is achieved solely by interaction between the ramp
structures 240 and 340.
With this arrangement, once the nut 210 has been threaded on the bolt shank
220 and tightened such that the ramp faces are in a mating condition, any
rotation of the nut 210 in the unthreading (loosening) direction will cause
relative
CA 02439416 2003-09-09
WO 01/66964 PCT/AUOI/00255
-18-
movement between mating ramp faces which will induce a wedge action that
jams the thread 230 of the nut 210 on the thread of the bolt shank 220. Not
only
does this action serve to lock the nut 210 against loosening, it also serves a
self-
tightening function.
The presence of the engaging face 396 is advantageous in that it allows a
wedging action with work-piece engagement through a flat surface without work-
piece embedding protrusions commonly used in prior art fasteners.
The threaded fastener assembly 100 described and illustrated in Figures 4 and
6
utilised a threaded fastener 210 in the form of a nut. The threaded fastener
210
could equally be in the form of a bolt 290 with the ramp structure 240
provided
on the head of the bolt, as shown in Figure 7.
Figure 8 illustrates a variant of the washer 390 of the first embodiment. The
variant is of similar construction to the washer 390, except that it
incorporates a
flange portion 790 providing an extended engaging face for engagement against
a work-piece.
Figure 9 illustrates another variant of the washer 390 of the first embodiment
and
Figure 10 illustrates a corresponding variant to the nut 290. In the first
embodiment, the ramp sections on the ramp structure 340 of the washer 390 and
the complementary ramp structures 240 on the nut 210 presented conical
contact surfaces. In the variant illustrated in Figure 9, the contact surface
341
presented by the ramp structure 340 is arcuate or spherical in the sense that
it
corresponds to part of the surface of a sphere. The contact surface 242
presented by the corresponding nut 210 is also arcuate or spherical.
Where the contact surfaces 242, 341 have been described as frusto-conical in
the first embodiment and arcuate or spherical in the variant thereto, it
should be
appreciated that they may be of any other appropriate shape including
variations
of cones and spheres.
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-19-
Referring now to Figures 11 to 15, there is shown a threaded fastener assembly
100 incorporating a washer 390 according to a second embodiment. The
washer 390 is in engagement with a work-piece 900. The threaded fastener
assembly utilised a threaded fastener 210 in the form of a nut. The nut 210
incorporates an engaging ramp structure 240 formed integrally therewith,
similar
to the embodiment previously described. The retainer washer 390 is in the form
of a frusto-conical spring rather than a plain washer as described in the
previous
embodiment. The spring washer 390 can be made of any commonly spring
material. The spring material is normally of greater hardness than that of the
bolt
or nut. The retainer washer 390 incorporates a ramp structure 340, which
interacts with the ramp structure 240 formed on the nut 210 in a manner
described in relation to the earlier embodiment. As best seen in Figure 12,
the
ramp structure 340, and in particular the sloping faces 345 thereof are
inclined
(skewed) along the radius inwardly away from the outer face 392. With this
embodiment, it is important to ensure that the frusto-conical spring is not
loaded
to an extent that it is fully deflected, but rather the deflection should
reach about
75% of full deflection at the required pre-load condition.
As best seen in Figure 13, the retainer washer 390 of this embodiment has an
outer periphery 391 configured for engagement with a tool such as a wrench.
As can be seen in Figure 11, the ramp structures 240, 340 are arranged to
initially engage each other at location (which is along the radius inner ends
of the
ramp structures) as the nut 210 is threaded onto the bolt. As the nut 210 is
tightened, and the retainer washer 390 resiliently deflects under loading, the
engagement between the ramp structures 240, 340 progressively increases in
the outward direction until full engagement is achieved.
Figure 16 illustrates a variant of the threaded fastener assembly 100 where
the
threaded fastener 210 is in the form of a bolt.
Referring now to Figures 17 to 20, there is shown a threaded fastener assembly
100 incorporating a retainer washer 390 according to a third embodiment. The
retainer washer 390 according to this embodiment is somewhat similar to the
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-20-
washer 390 of the previous embodiment in that it also uses a frusto-conical
spring. However, the mechanical connection provided between the bolt 210 and
the retainer washer 390 is not by way of interacting wedge ramps, as was the
case with previous embodiments, but rather by way of interacting ratchet
teeth.
More particularly, in this embodiment the threaded fastener 210 is in the form
of
a bolt provided with a ramp structure 240 comprising ratchet teeth 248 on a
boss
portion 249 formed at the junction between the bolt head 210 and bolt shank
220. The ramp structure 240 is adapted to interact with complimentary ramp
structure 340 provided on retainer washer 390, the ramp structure 340 also
comprising ratchet teeth 348. A rounded engaging face 397 is formed on the
edge of the retainer washer 390 where it contacts the work-piece 400 to avoid
damage to the work-piece.
The initial engagement between dished and protruding ramp structures 240, 340
can cause immediate alignment of their surfaces. As can be seen in Figure 14,
the ratchet teeth of ramp structures 240, 340 are arranged to initially engage
each other at a location along the radially inner ends of the two ramp
structures,
as shown in Figure 19. As the nut 210 is tightened and the retainer washer 390
resiliently deflects under loading, the engagement between the ramp structures
240, 340 progressively increases until full engagement is achieved, as
illustrated
in Figure 20.
In the threaded fastener assembly 100 of this embodiment, the threaded
fastener
210 is a bolt. In a variant illustrated in Figure 21, the threaded fastener
210 is a
n ut.
Figures 22 and 23 illustrate a threaded fastener assembly 100 incorporating a
retainer washer 390 having an alternative configuration of ratchet teeth 348.
In
this embodiment the teeth of ramp structure 340 are of arcuate or spherical
shape, rather than conical shape, as also are the teeth of the complementary
ramp structure 240 on the threaded fastener 240. The ratchet teeth 248 on the
bolt 210 are of a complimentary configuration. It should, however, be
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-21 -
understood that the ratchet teeth can be of any appropriate complimentary
configuration.
As can be seen from Figure 22, the two ramp structures 240, 340 initially
engage
each other at a location adjacent their radially inner ends. As the threaded
fastener 210 is tightened and the retainer washer 390 resiliently depicts
under
loading, engagement between the ramp structures 240, 340 progressively
increases until full equipment is achieved, as illustrated in Figure 23.
Washers according to the previous embodiments have been incorporated into
bolted assemblies 100 which used ramp structure interaction of two components;
namely, a threaded fastener 210 (being either a bolt or a nut) and the
retainer
washer 390 incorporated therein. There are situations in certain applications
where it is advantageous to introduce a third component, (or indeed still more
components) into the threaded fastener assembly.
One such arrangement is illustrated in Figures 24 to 27 involving a threaded
fastener assembly 100 incorporating two wedge ramp washers 390, 490 in
accordance with a fifth embodiment. Two sets of ramps (protruding and dished)
are formed in parallel adjacent inner and outer faces 391, 392 as shown in
Figure 27. Depicted here are wedge ramps, but the design is equally
appropriate
for ratchets teeth. One of the washers functions as the retainer washer 390
and
the other functions as an intermediate washer 490. The two washers of this
embodiment, which are in the form of spring washers, are positioned in series
and used with a conventional bolt and nut (without ramp structures). The
spring
deflection of the assembly is a sum of deflections of the two spring washers.
Operation is similar to previously described embodiments, except that the
intermediate washer 490 and a traditional threaded fastener 210 replace the
threaded fastener with a ramp structure incorporated on it. Although washers
390, 490 are each depicted with double sets of ramp structures (one on each
side of the washer), only one ramp structure on each washer will be used for
serial engagement as described.
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-22-
Referring to Figures 28 to 31, there is shown a threaded fastener 210
incorporating two identical spring wedge ramp washers, one washer 390
functioning as a retainer washer and the other washer 490 functioning as an
intermediate washer. The design equally applies to ratchet teeth. Both the
intermediate washer 490 and the retainer washer 390 have two sets of ramp
structures 441, 442 and 341, 342 respectively. The ramp structure 441 is
located about the central aperture adjacent the inner face 491, while the ramp
structure 442 is located about the central aperture adjacent the outer face
492.
The ramps 442 interact with the corresponding wedge ramps of the threaded
fastener 210, while ramps 342 and the outer face 392 of the retainer washer
390
fit snugly into ramps 441 and the inner face 491 of the intermediate washer
490
preventing relative rotation between the intermediate washer and the retainer
washer. The intermediate and retainer washers act effectively as two spring
washers in parallel, doubling the deflection force. It should be understood
that
two or more spring washers might be employed, with the spring washers
arranged in any combination involving series or parallel relationship.
Figures 32 to 36 relate to a threaded fastener assembly 100 comprising a
threaded fastener 210 in the form of a nut, an intermediate washer 490 and a
retainer washer 390. Alternatively, a bolt 290 as illustrated in Figure 37 can
substitute for the nut 210.
The intermediate washer 490 has two sets of ramps 442, 441 which interact with
corresponding sets of ramps 240, 340 on the threaded fastener 210 and the
retainer washer 390.
The set of ratchet ramps 441 on the intermediate washer 490 protrudes into the
dished set of ratchet ramps 340 on the retainer washer 390. The other side of
the retainer washer 390 is provided with an undercut section 397, which
defines
an annular engaging face 396 in the fashion of the first embodiment. The
relative positioning of the ratchet ramps 340, 441 is such that they are at or
about the same radial distance from the axis of rotation of the nut 210 as
wedge
ramps 442,240. Typically, the ratchet ramps 340, 441 have a locking
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-23-
configuration, which is in reverse to that of the wedge ramp structure 442 and
240 on the intermediate washer 490 and the nut 210. The purpose of the
retainer washer 390 is to frictionally engage the work-piece so as to allow
smooth and effortless operation of the nut 210 and intermediate washer 490 on
tightening of the threaded fastener and affording protection for the surface
of the
work-piece in which it is in contact.
The fact that the ratchets will undergo some flattening during preloading
should
be taken into consideration during manufacturing. Where the washers are
manufactured by a punching operation, sufficient material should be provided
so
that ratchets are hardened as required during the punching operation.
Additional
hardening could be achieved during preloading. Where the washers are
manufactured by a cutting operation, the design should provide a ratchet shape
which after flattening during preloading has sufficient ratchet height to
prevent
fastener rotation against the ratchets. The design could be improved by
increasing height of the ratchets towards fastener axis where loads are the
greatest.
It must be understood that similar intermediate washer with dished ratchet set
and protruding wedge set can be built to display similar operational qualities
when assembled with a washer of the first embodiment and a nut of the fourth
embodiment.
It should be noted that the contact between the threaded fastener 210 and the
intermediate washer 490, as well as between the intermediate washer 490 and
the retainer washer 390, is solely through the interacting ramps 240, 442 and
441, 340 respectively.
Figures 39 to 42 illustrate a threaded fastener assembly 100 incorporating an
intermediate washer 490 and a retainer washer 390 of the type employed in the
previous embodiment. The assembly 100 is similar to the previous embodiment,
except that the intermediate washer 490 is of larger diameter and a visual
indication of the extent to which the threaded fastener assembly is loaded is
provided. The threaded fastener assembly 100 is illustrated in four operating
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-24-
positions that start after initial threading engagement, as shown sequentially
in
the four views. The first position, which is shown in Figure 39, has threaded
fastener 210 engaged with the intermediate washer 490 via wedge ramps and
intermediate washer engaged with the retainer washer 390 via ratchet ramps.
The retainer washer has just established frictional connection with a work-
piece
Further threading on of the fastener 210 continues while the intermediate
washer
490 rides over the ratchet ramps interacting between the intermediate washer
and the retainer washer until a desired preload is reached as illustrated in
the
second position depicted in Figure 40. The preload is determined in accordance
with a scale described later. If further adjustment of the loading is desired,
it
could be achieved at this point with little effort by a wrench engaging the
intermediate washer 490 and driving it further in the threading on direction.
Loading now takes place on wedge ramps and not on the thread, while being
prevented from backing off by ratchet ramps. A third position depicted in
Figure
41, shows additional loading achieved in this manner. Figure 42 illustrates
the
fourth position where the threaded fastener 210 was turned in the unscrewing
direction under an influence such as dynamic forces arising from vibration,
and
loosening on the thread was offset by further tightening between the ramp
structure on the threaded fastener and the interacting ramp structure on the
intermediate washer 490. In such a dynamic environment, the nut will be turned
in both directions and when any slack occurs in the assembly it will be
eliminated
automatically through the travel on the ratchet teeth. The nut 210 has a
pointer
260 which operates in association with a scale 450 on the intermediate washer
490 thereby to provide the visual indication of loading. Similarly, the
intermediate washer 490 has a pointer 460, which operates in association with
a
scale 350 on the retainer washer 390. The total loading of the threaded
fastener
assembly 100 at any operational position can be displayed on the scales. The
threaded fastener assembly 100 is released simply by rotating intermediate
member 490 in a counter clockwise direction to primarily release the wedge
loading and later unthread the nut.
For fastener removal purposes, where one tool engages two parts of the
assembly, a size adaptor 500 (as shown on Figure 38) is provided. The size
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-25-
adaptor 500 is arranged to fit onto the nut 210 to enable a tool to turn the
nut and
the retainer washer in unison. Constructing the nut 210 with an outer
periphery of
a different size than the outer periphery of the retainer washer 390 allows
tool
engagement with separate pieces of the assembly. It can also serve as a
security feature as different size and shape tools would otherwise need to be
used for tightening and removal of the fastener assembly.
Referring now to Figures 43 to 48, there is shown a threaded fastener assembly
100 that includes a threaded fastener 210 and a retainer washer 390. The
washer 390 incorporates wedge ramps and a scale is similar to plain retainer
washers of previous embodiments, as well as provision to grip the washer for
manual operation as will be explained later.
As best seen in Figures 44 and 47, there is a provision for a mechanical
connection between the nut 210 and the retainer washer 390. The provision
comprises a wedge ramp structure 240 formed integrally with the nut 210 and an
interacting section ramp structure 340 formed integrally with the retainer
washer
390. As was the case in the earlier embodiments, the retainer washer has an
inner face 391 with an undercut section providing a central recess 397
surrounded by an annular engaging face 396. The annular engaging face 396 is
spaced along the radius further from the axis of rotation of the nut 210 than
is the
mechanical connection provided by the interacting ramp structures 240, 340.
The nut 210 and wedge washer 390 are assembled as a unit and retained in that
condition by way of a plain conventional washer 890. While the washer 890
retains the nut 210 the retainer washer 390 in the assembled condition, it
does
allow limited axial movement and free relative rotation.
A scale 350 is provided to allow a visual indication of the amount of load
imposed on the threaded fastener assembly 100 through the wedging action of
the interacting ramp structures 240, 340.
The threaded fastener assembly 100 incorporates a gripping means 270 in the
form of a plastic grip, which is connected to the nut 210 to allow rotation of
the
nut by hand. Similarly a further gripping means 370 in the form of plastic
grip is
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-26-
provided to operate the retainer washer 390. This is particularly useful as it
allows the threaded fastener assembly to be tightened and released manually
without requiring use of tools.
A particular application of the threaded fastener assembly 100 of this
embodiment is for securing a grinding disk onto the drive spindle of a power
tool
such as an angle grinder. The grinding disk would be clamped between a back
flange joined integrally with the spindle of the power tool and the inner face
391
on the retainer washer. In such applications, it is possible for the rise
angle of the
sloping faces 345 to be less than the lead angle of the spindle thread. The
appropriate selection of the rise angle ensures motor tightening of the
threaded
fastener assembly through interaction of the ramp structures rather than on
the
thread of the nut 210. In a typical installation, the nut 210 is screwed onto
the,
thread of the spindle and secured tightly through manual operation of the grip
270. The abutment faces 246, 346 of the ramp sections in the two ramp
structures convey the tightening torque. Upon operation of the motor, the ramp
structure 240 on the nut is caused to ride on the ramps 340 of the retainer
washer 390. The fully loaded position is depicted on Figures 46 to 48.
Provided
that the threaded fastener assembly 100 was properly tightened prior to
operation of the motor, very little or no further tightening on the thread
occurs.
Upon a sudden stop of the motor, the inertia of the disc will cause the ramp
structure 240 on the nut 210 to ride down the ramp structure 340 on the
retainer
washer 390 and release tension in the connection. On the other hand, upon
stopping of the motor in a slow and controlled fashion, the tension in the
connection is not released but the amount of torque required to turn a nut
with a
spindle rotating freely down the ramps is within possibilities of manual
operation.
Consequently turning the grip 370 of the retainer washer 390 in thread
unscrewing direction will allow disassembly.
It happens on occasion that as a consequence of a sudden stop a conventional
locking nut can detach from the shaft with which it is engaged and in so doing
allow the disc to separate from the drive spindle together with the disc. The
threaded fastener assembly 100 of Figures 49 to 59 seeks to prevent such
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-27-
detachment. The assembly 100 utilises an intermediate washer 490 and a
retainer washer 390 incorporating gripping means for manual operation. The
assembly 100 is shown in its initial position in Figures 49 to 51. The
threaded
fastener 210 in the form of a nut, the intermediate washer 490 and the
retainer
washer 390 are fitted together and retained as a unit, in a similar fashion to
the
previous embodiment. This assembly would be much easier to secure manually
than a two-piece, as only fraction of the torque is required for turning the
nut on a
lesser radius along the ratchets.
Figures 52 to 60 illustrate subsequent operational positions equivalent to
these
described with relation to Figures 39 to 42.
The safety feature of this assembly can best be described with relation to
Figure
60 which shows schematically the relative position of ramps during steady
motor
operation of the power tool. At a sudden stop condition of the motor, the disc
will
still tend to turn with the retainer washer, but the ratchet connection
ensures that
the intermediate member with the nut is not torque in the unscrewing
direction.
Excellent operational capabilities could also be achieved for the same
application
when intermediate washer of this embodiment is flipped; that is, the ratchet
connection appear between it and the nut.
It should be understood that scales can be employed on all previously
described
embodiments.
Any threaded fastener assembly utilising ratchet teeth is particularly
suitable for
the implementation of a scale to provide a visual indication during pre-
loading.
The use of ratchet teeth has two advantages. It allows effortless tightening
of
the assembly and automatically aligns the pointer 260 on the nut with the
beginning of the scale 350. Human error is thus eliminated for angle
controlled
tightening to achieve 'finger tight' position.
A particular advantage of the threaded fastener assemblies according to the
invention is that they can be positioned in an array and a common tool
employed
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-28-
to operate the fasteners in unison. Such an arrangement for a circular array
is
illustrated in Figures 56 and 57 of the drawings.
Referring in particular to Figure 61, there is shown a series of five bolted
assemblies 100 which are positioned in a circular array and which employ
washers according to the invention. The threaded fasteners 210 have an along
the radius outer periphery 213 equipped with engaging means 280 configured to
mate with engaging means 680 located on the internal wall of the loading
structure. The loading structure 690 is fitted around the array. The loading
structure 690 has a recess 687 for receiving a wrenching tool (not shown).
Turning the loading structure with the aid of the wrenching tool engaged in
the
recess 687 allows operation of the various threaded fastener assemblies 100 in
unison.
Referring now to Figure 62 of the drawings, there is illustrated a similar
arrangement with the exception that there is provided a loading structure 690
formed with circumferentially spaced engaging surfaces 280 and 680 which
operate five threaded fastener assemblies 100 at a time in a prescribed
sequence upon rotation of the tool.
Loading several fastener assemblies in unison that is possible with the use of
the
loading structure 690 and low tightening torque fastener assemblies 100 is
further enhanced by the amount of required preload printed on the structure
for
each set of five fastener assemblies. Similar to scales on individual
fasteners,
the printing could be in a form of sticky labels.
The amount of calculated preload could be printed on a loading structure for
one
or more passes and may be different for applications with or without gaskets.
Although the embodiments of Figures 61 and 62 are depicted with fastener
assemblies in a circular array, the invention is not limited to circular
arrays.
The array loading techniques currently in uses including incremental
tightening
and Van Campen's matrix could be applied in conjunction with equipment
according to the present invention.
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-29-
Consequently it has been envisaged a precision loading of arrays that makes
use of this invention to be extended to include installations lesser than
critical.
Unlike many prior art fastener devices, the threaded fastener assemblies that
incorporate washers according to the present invention use most of the
tightening torque as preload on the assembly.
Loading the fastener assembly on the ramp structures can eliminate unknown
friction between the fastener assembly and the work-piece. It would be
advantageous to lower the frictional coefficient between the ramp structures
by
use of lubricants and other techniques. It is believed that such arrangements
that
accompany special geometry that characterize the washers of this invention may
allow the same preload to be achieved with only about 20% of torque required
as
compared to prior art fasteners. Such a reduction of tightening torque allows
operation of the threaded fastening assemblies without external tools, or
simultaneous tightening of a circular array of fasteners as described.
It should be appreciated that the scope of the invention is not limited to the
scope
of the particular embodiments described. While various features of the
invention
have been introduced in relation to the description and drawings of particular
embodiments, it should be understood that those features needed not be limited
to those particular embodiments. Features of the invention can be in any
combination as may be appropriate on any threaded fastener assembly
employing washers according to the invention.
The threaded fastener assemblies employing washers according to the present
invention aim to address at least some of the deficiencies of the present art.
It is
believed that threaded fastener assemblies incorporating washers according to
the invention exhibit superiority in areas of safety, reliability and
maintainability is
due to a combination of the following advantages:
(1) Dramatically improved accuracy of preloading with the use of enhanced
angle controlled tightening;
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-30-
(2) Counteracting elevated and differential temperature effect and creep
and importantly not contributing towards it with the use of improved
conical spring washers;
(3) Counteracting off-torque by wedging action;
(4) Dynamic and elastic behaviour of the fastener contributes substantially
to its ability to hold, add and release preload automatically and as
required, according to the environmental conditions of the joint;
(5) Ease of accurate loading with incorporation of the scale;
(6) Effortless loading with reduction of required torque and use of friction
reducing techniques;
(7) Reduction or elimination of galling, sizing and gouging of most of the
abutting surfaces;
(8) Self-centering characteristic allows a reduction in bolt size for a
prescribed external load and negligible residual torque after loading;
(9) The capacity for manual operation due to reduced torque requirement;
(10) The ability of unison loading of multi-fastener assemblies beneficiary of
the reduced torque;
(11 ) Thread striping prevention due to even load distribution along the
threads;
(12) Elimination of hoop spreading due to conical force transfer surface;
(13) Prevents over-tightening of the disc o as power tool due to loading on
wedges rather than on threads;
CA 02439416 2003-09-09
WO 01/66964 PCT/AU01/00255
-31 -
(14) Prevents unintentional detachment of the disc of a powertool in the
event of a sudden halt of the motor in powertools due to ratchet action;
(15) Allows manual attachment and detachment of the disc of a powertool
as it utilizes motor action for both tightening and release on wedges;
(16) Can be produced from commonly used materials for both plain
washers and spring washers;
(17) All the common methods used for the production of known washers
can be utilised.
Throughout the specification, unless the context requires otherwise, the word
"comprise" or variations such as "comprises" or "comprising", will be
understood
to imply the inclusion of a stated integer or group of integers but not the
exclusion of any other integer or group of integers.
